Conventionally, there have been developed techniques for forming a hard film on a base material by using a physical vapor deposition method, such as that represented by ion plating. Among these films, a TiN film has been put to practical use most widely, and used for tools, metal molds, and spectacles and other accessories. However, since this film begins oxidizing at 500° C. or higher, it cannot be used for parts, tools, molds, and the like which are exposed to high temperatures. As a solution to this problem, a TiAlN film has been developed. This film can be used even at high temperatures up to about 800° C. because of restrained oxidation, but at temperatures higher than 800° C., like the aforementioned TiN film, it is difficult to use because it is deteriorated by oxidation.
On the other hand, an Al—Cr—N film has been proposed as a film capable of being used at high temperatures. This film can be used at high temperatures up to about 1000° C. (refer to Japanese Patent Provisional Publication No. 10-25566 (No. 25566/1998)). However, this film has a problem with its adhesiveness, and also has a problem of wear resistance when it is used for products and parts that are subjected to a high load. To obtain a hard film having oxidation resistance, studies have been carried out to improve the wear resistance of Al—Cr based nitrides. However, a film having sufficient performance has not yet been obtained from the viewpoint of adhesive force and the adhesive properties of film adhering to an object to be treated.